Universal soldering station controller

[KL27x]

OK. "Tip heats (more) rapidly". Ahh, ok. I think what you meant is that PID allows the tip to drop less in temp upon initial contact because it starts to heat with less latency (on average). PID is improving performance thru this, and thru the correction of temp differential btn sensor and tip.

I apparently have to answer my own questions because I'm the only one not bridging the obvious gaps. I'm sure this post doesn't even make sense to anyone. But something clicked (which might even be correct), and this discussion has been helpful, in any case.

[Kalvin]

Here is a nice animation on how the parameters of the PID change the performance of the control loop:

https://en.wikipedia.org/wiki/PID_controller#Manual_tuning

[KL27x]

The part that wasn't clicking before was in the practical application as regarding the iron.

What I am connecting, now, is that the undershoot of the non PID iron is almost always going to happen when you first touch the joint. This is because the nonPID iron essentially lives in the "over" area for over 90% of the time while the tip is not touching anything. Tip slowly cools, heater goes on for just an instant. Tip goes back to slowly cooling. Slowly cooling in the "over" is the usual state.

So when you touch the joint, the first dip/undershoot is going to be larger than it could be with PID. Of course the blind squirrel could find the nut... and the heater could be just about to come on at the same time as you touch the joint... so that the oscillation is minimized by chance. But this is not going to be the norm.

 
So minimizing undershoot is one of the two key improvements in my current understanding (which is subject to change). The other being the correction for difference in temp between tip and sensor... which amounts to temperature droop that increases with thermal load, if I understand correctly. These are the two things I would be focusing on with an algorithm for a soldering iron. Overshoot I'm ok with. I'm going to focus on quickest response and err on more heat. Once the iron is in action, I want the tip to respond faster to retain more heat/temp and then continue on to hot or hotter and either one is fine.

[OGESON]

What?      After reading these posts about the soldering station I am at a loss as too why you don't just spend $50.00 and buy a hot air and iron station combo on EBay. I have two and they work fine. Now you can have fun building all the other projects you have in your bucket list.
My projects are Tube ( VALVE ) Amps for audio.  I left PID at work when I retired as an Industrial Electrical Maintenance Tech.
Keep up the good work Guys.  I love all this stuff.

Jim OGESON

[DBecker]

What?      After reading these posts about the soldering station I am at a loss as too why you don't just spend $50.00 and buy a hot air and iron station combo on EBay. I have two and they work fine. Now you can have fun building all the other projects you have in your bucket list.
My projects are Tube ( VALVE ) Amps for audio.  I left PID at work when I retired as an Industrial Electrical Maintenance Tech.

I have one of those inexpensive soldering stations.

They are far better than old-style fixed wattage soldering iron, but still fall short of what is possible.  They are clearly cheating on their heat-up time and stability.  The display counts up to the set temperature, and stays perfectly stable at that temperature.  Even while the tip clearly takes longer to heat, and is slow to respond to thermal load.

[stj]

this is what to aim for!
https://www.youtube.com/watch?v=u588sh-4thg&feature=youtu.be